This electrodialysis apparatus can be used in a number of large scale process applications. Specifically, it may be used for the recovery of lactic acid from fermentation derived ammonium lactate in a two compartment cation cell. There may be either a nanofilter or an ion exchange column (or both) in communication with the base loop of the cation cell. The column contains a weak acid cation exchange resin.
For more information on the background of the inventive structure, reference may be made to my co-pending applications shaving the following identifications: Process for the Recovery of Organic Acids and Ammonia from Their Salts, Ser. No. 08/639,831, filed Apr. 29, 1996 now U.S. Pat. No. 5,814,498; Electrodialysis Apparatus, Ser. No. 08/784,050, filed Jan. 17, 1997 (now U.S. Pat. No. 5,972,191); and Gasket and Apparatus for Deionization, Ser. No. 08/785/648, filed Jan. 17, 1997 now U.S. Pat. No. 6,123,823.
The invention includes an apparatus and its related method using an electrodialysis cell (or cells) in combination with a nanofiltration unit for filtering an incoming monovalent salt solution in order to minimize the level of multivalent impurities. The apparatus may also include an electrodialysis cell (or cells) in combination with an ion exchange column in communication with a base loop of the said electrodialysis cell. The pH of the base product from the apparatus is preferably in the range of 7 to about 13.5.
The apparatus and process are particularly well suited to the production of acids, especially organic acids, in conjunction with weak bases such as ammonia, or the salts of weak acids such as sodium carbonate or sulfite. The electrodialysis cells of the invention may employ membranes, such as bipolar membranes, or assemblies for splitting water. Alternatively the splitting of water for acid, base production may be accomplished with a set of electrodes.